This invention relates to matrix addressable display devices, and more particularly to a method and apparatus for testing the emission of the display.
Quality assurance requires the testing of manufactured products to determine if they will function over a given set of parameters. Testing is performed on a random sampling of products from the production lines, or in some industries, on every product which is manufactured.
Optical measurements are currently performed on display devices at the final stages of display testing. Optical measurement is accomplished by turning on all the cathode emitters in a pixel, and visually observing them. This method is extremely subjective, as it relies on the judgement of the individual peering at the screen.
Photon Dynamics of Milipitas, Calif. employs a method in which photons from a full display (i.e., substantially all of the pixels are turned xe2x80x9conxe2x80x9d at the same time) are measured. A completed display device is optically tested by measuring the light emitted from the display.
There are several drawbacks to the above described optical method. For example, the process is very expensive, as it requires sophisticated optics and processing algorithms in order to determine the relative number of functional pixels.
Additionally, the optical systems require closely spaced anodes with respect to the cathode in order for the inspection optics to obtain accurate measurements. Therefore, the optical systems are not practical for testing display baseplates prior to their assembly in a field emission device.
Other methods used to measure current emitted by field emitter devices employ a positively biased electrode. However, these methods also measure the total current emitted by substantially all of the pixels in the completed unit. Therefore, these methods are also limited to measuring the operation of the device as a whole.
There still exists a need for a method to measure the current emitted by individual pixels in the display in order to determine their functionality, as well as the total number of functioning pixels (also known as the xe2x80x9cyieldxe2x80x9d). Additionally, manufacturing realities require that the functionality of the individual pixels is measured in a rapid fashion.
According to one embodiment of the present invention, an assembly useful for testing emissive cathodes includes a collector, a wafer support device for releasably supporting a wafer opposite the collector, and contact pins for contacting the wafer located above the wafer support device and for testing a number of emissive cathodes located on the wafer. A high vacuum exists between the collector and the wafer support device.
According to another embodiment of the present invention, a testing apparatus useful for measuring emitted current includes a socket in which to dispose a substrate having cathodes, an anode disposed opposite the socket for collecting emissions from the cathodes, and contact pins disposed in the socket for making contact with the substrate. A high vacuum exists between the socket and the anode.
According to another embodiment of the present invention, a wafer probe station useful for testing wafers under vacuum includes a probe chamber including a probe card and a testing stage. The probe card has pins and an anode plate having a luminescent film. The testing stage, disposed opposite the probe card, includes a socket for releasably supporting the wafers.